The new photodiodes with cut-off wavelengths at 3640 nm, 4600 nm and 5150 nm have been recently developed in a
high-tech company LED Microsensor NT (St.Petersburg, Russia) in cooperation with Aalto University (Espoo, Finland).
Photodiode (PD) heterostructures InAsSb/InAsSbP were grown by MOVPE on InAs substrates. For the PDs with a cutoff
wavelength at 3640 nm at room temperature the responsivity at 3300 nm reached 1.46 A/W and, detectivity was
1.56*1010 cm.Hz1/2/W. For the PDs with a cut-off 4600 nm the same parameters were: 1.91 A/W and 6.7*109 cm.Hz1/2/W respectively (lambda=4100 nm). For the third type of PDs with a cut-off at 5150 nm responsivity was 0.29 A/W, detectivity was 4.2*108 cm.Hz1/2/W (lambda=5000 nm).
Creation of photodiodes for the spectral range 2500-5200 nm with acceptable efficiency in photovoltaic operation mode
(with no reverse bias) and using them in a pair with spectrally matched LEDs driven by very short current pulses allows
developing optical cells with very low power consumption (less than 1 mW). Small size of the LED and PD dies (0.4-0.8
mm) and low heating makes it possible to design very thin optical cells (less than 2 mm) for measuring CH4, CO2, CO,
H2O and other substances . Mounting of a few LED dies that emit at different wavelengths in such a small cell allows
measuring different chemical substances simultaneously. Direct coating of optical filters on the LED or PD surface
during post-growth process allows improving selectivity and sensitivity of the sensor.
Super low power consumption of the diode-based optical cells makes them promising candidates for the wireless mesh
sensor networks for various gas monitoring purposes as well as for HVAC systems. Combination of the low power
consumption and thin size of the cells opens possibility to embed them in mobile devices.